Cracking in new bathroom floor tiles - cause? - update

hc25036

Fitter has been on holiday, then we were. Came round and was nice as pie. Reckons that there will be a join in the ply under the crack, so he will buy some more tiles and get his tiler back to identify the problem properly and fix it.

I thought this guy's quote was a little high, but looks like it was a good call to give him the job.

sutwam

Taking up the tiles and laying new ones is a good result - but what are they going to do to stop it from happening again?

hc25036

The plan is to lift the tiles and diagnose the problem before refitting.

sutwam

Just a few notes for you to be prepared for the site visit.

The crack is being caused my movement in either verticle or horizontal plain.

If it's horizontal (i.e. the floorboards expanding and contracting) the installation should have been done with either, as previous posts have said, at least 12mm plywood screwed down every 6 inch centres, again as mentioned before - backerboards, or a decoupling membrane (3mm depth)

If movement is in the verticle plain (i.e. when 2 different subfloor butt each other or there is bounce in the floor) then a movement joint or a flexible compound such as mastic should be used in the tile layer above the joint.

Has anything altered from your previous tiles to the new ones? Are they large format? Did you have underfloor heating (UFH) installed? If yes to either of these then perhaps stress cracks.

If large format tiles was the correct grout line widths used? Different tile manufacturers recommend differnt widths, the tile shop should be able to tell you this.

On UFH the Tiling Association recommends if using UFH at least a 3mm grout line needed, some kind of under tile decoupling is needed and movement joints in maximum fields of 3.5m x 3.5m